Support for shifted port-ranges in DNAT was added to iptables in 2018.
This allows one to redirect packets intended for one port to another in
a range in such a way that the new port chosen has the same offset in
the range as the original port had from a specified base value.
For example, by using the base value 2000, one could redirect packets
intended for 10.0.0.1:2000-3000 to 10.10.0.1:12000-13000 so that the old
and new ports were at the same offset in their respective ranges, i.e.:
10.0.0.1:2345 -> 10.10.0.1:12345
However, while support for this was added to the common NAT infra-
structure in the kernel, only the xt_nat module was updated to make use
of it. This support has now also been added to the nft_nat module, so
make it available in user space.
In contrast to iptables, where shifting is only available for DNAT, both
DNAT and SNAT are supported.
Signed-off-by: Jeremy Sowden <jeremy@xxxxxxxxxx>
---
include/libnftnl/expr.h | 1 +
include/linux/netfilter/nf_tables.h | 2 ++
src/expr/nat.c | 22 ++++++++++++++++++++++
tests/nft-expr_nat-test.c | 4 ++++
4 files changed, 29 insertions(+)
diff --git a/include/libnftnl/expr.h b/include/libnftnl/expr.h
index 9873228dd794..e118a57d4769 100644
--- a/include/libnftnl/expr.h
+++ b/include/libnftnl/expr.h
@@ -150,6 +150,7 @@ enum {
NFTNL_EXPR_NAT_REG_PROTO_MIN,
NFTNL_EXPR_NAT_REG_PROTO_MAX,
NFTNL_EXPR_NAT_FLAGS,
+ NFTNL_EXPR_NAT_REG_PROTO_BASE,
};
enum {
diff --git a/include/linux/netfilter/nf_tables.h b/include/linux/netfilter/nf_tables.h
index 4608646f2103..5c7a47ac8746 100644
--- a/include/linux/netfilter/nf_tables.h
+++ b/include/linux/netfilter/nf_tables.h
@@ -1415,6 +1415,7 @@ enum nft_nat_types {
* @NFTA_NAT_REG_PROTO_MIN: source register of proto range start (NLA_U32: nft_registers)
* @NFTA_NAT_REG_PROTO_MAX: source register of proto range end (NLA_U32: nft_registers)
* @NFTA_NAT_FLAGS: NAT flags (see NF_NAT_RANGE_* in linux/netfilter/nf_nat.h) (NLA_U32)
+ * @NFTA_NAT_REG_PROTO_BASE: source register of proto range base offset (NLA_U32: nft_registers)
*/
enum nft_nat_attributes {
NFTA_NAT_UNSPEC,
@@ -1425,6 +1426,7 @@ enum nft_nat_attributes {
NFTA_NAT_REG_PROTO_MIN,
NFTA_NAT_REG_PROTO_MAX,
NFTA_NAT_FLAGS,
+ NFTA_NAT_REG_PROTO_BASE,
__NFTA_NAT_MAX
};
#define NFTA_NAT_MAX (__NFTA_NAT_MAX - 1)
diff --git a/src/expr/nat.c b/src/expr/nat.c
index ca727be0cda6..6d304870d419 100644
--- a/src/expr/nat.c
+++ b/src/expr/nat.c
@@ -29,6 +29,7 @@ struct nftnl_expr_nat {
enum nft_registers sreg_addr_max;
enum nft_registers sreg_proto_min;
enum nft_registers sreg_proto_max;
+ enum nft_registers sreg_proto_base;
int family;
enum nft_nat_types type;
uint32_t flags;
@@ -59,6 +60,9 @@ nftnl_expr_nat_set(struct nftnl_expr *e, uint16_t type,
case NFTNL_EXPR_NAT_REG_PROTO_MAX:
memcpy(&nat->sreg_proto_max, data, sizeof(nat->sreg_proto_max));
break;
+ case NFTNL_EXPR_NAT_REG_PROTO_BASE:
+ memcpy(&nat->sreg_proto_base, data, sizeof(nat->sreg_proto_base));
+ break;
case NFTNL_EXPR_NAT_FLAGS:
memcpy(&nat->flags, data, sizeof(nat->flags));
break;
@@ -94,6 +98,9 @@ nftnl_expr_nat_get(const struct nftnl_expr *e, uint16_t type,
case NFTNL_EXPR_NAT_REG_PROTO_MAX:
*data_len = sizeof(nat->sreg_proto_max);
return &nat->sreg_proto_max;
+ case NFTNL_EXPR_NAT_REG_PROTO_BASE:
+ *data_len = sizeof(nat->sreg_proto_base);
+ return &nat->sreg_proto_base;
case NFTNL_EXPR_NAT_FLAGS:
*data_len = sizeof(nat->flags);
return &nat->flags;
@@ -116,6 +123,7 @@ static int nftnl_expr_nat_cb(const struct nlattr *attr, void *data)
case NFTA_NAT_REG_ADDR_MAX:
case NFTA_NAT_REG_PROTO_MIN:
case NFTA_NAT_REG_PROTO_MAX:
+ case NFTA_NAT_REG_PROTO_BASE:
case NFTA_NAT_FLAGS:
if (mnl_attr_validate(attr, MNL_TYPE_U32) < 0)
abi_breakage();
@@ -163,6 +171,11 @@ nftnl_expr_nat_parse(struct nftnl_expr *e, struct nlattr *attr)
ntohl(mnl_attr_get_u32(tb[NFTA_NAT_REG_PROTO_MAX]));
e->flags |= (1 << NFTNL_EXPR_NAT_REG_PROTO_MAX);
}
+ if (tb[NFTA_NAT_REG_PROTO_BASE]) {
+ nat->sreg_proto_base =
+ ntohl(mnl_attr_get_u32(tb[NFTA_NAT_REG_PROTO_BASE]));
+ e->flags |= (1 << NFTNL_EXPR_NAT_REG_PROTO_BASE);
+ }
if (tb[NFTA_NAT_FLAGS]) {
nat->flags = ntohl(mnl_attr_get_u32(tb[NFTA_NAT_FLAGS]));
e->flags |= (1 << NFTNL_EXPR_NAT_FLAGS);
@@ -192,6 +205,9 @@ nftnl_expr_nat_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
if (e->flags & (1 << NFTNL_EXPR_NAT_REG_PROTO_MAX))
mnl_attr_put_u32(nlh, NFTA_NAT_REG_PROTO_MAX,
htonl(nat->sreg_proto_max));
+ if (e->flags & (1 << NFTNL_EXPR_NAT_REG_PROTO_BASE))
+ mnl_attr_put_u32(nlh, NFTA_NAT_REG_PROTO_BASE,
+ htonl(nat->sreg_proto_base));
if (e->flags & (1 << NFTNL_EXPR_NAT_FLAGS))
mnl_attr_put_u32(nlh, NFTA_NAT_FLAGS, htonl(nat->flags));
}
@@ -258,6 +274,12 @@ nftnl_expr_nat_snprintf(char *buf, size_t remain,
SNPRINTF_BUFFER_SIZE(ret, remain, offset);
}
+ if (e->flags & (1 << NFTNL_EXPR_NAT_REG_PROTO_BASE)) {
+ ret = snprintf(buf + offset, remain,
+ "proto_base reg %u ", nat->sreg_proto_base);
+ SNPRINTF_BUFFER_SIZE(ret, remain, offset);
+ }
+
if (e->flags & (1 << NFTNL_EXPR_NAT_FLAGS)) {
ret = snprintf(buf + offset, remain, "flags 0x%x ", nat->flags);
SNPRINTF_BUFFER_SIZE(ret, remain, offset);
diff --git a/tests/nft-expr_nat-test.c b/tests/nft-expr_nat-test.c
index 3a365dd307c2..1204c4b7be62 100644
--- a/tests/nft-expr_nat-test.c
+++ b/tests/nft-expr_nat-test.c
@@ -49,6 +49,9 @@ static void cmp_nftnl_expr(struct nftnl_expr *rule_a,
if (nftnl_expr_get_u32(rule_a, NFTNL_EXPR_NAT_REG_PROTO_MAX) !=
nftnl_expr_get_u32(rule_b, NFTNL_EXPR_NAT_REG_PROTO_MAX))
print_err("Expr NFTNL_EXPR_NAT_REG_PROTO_MAX mismatches");
+ if (nftnl_expr_get_u32(rule_a, NFTNL_EXPR_NAT_REG_PROTO_BASE) !=
+ nftnl_expr_get_u32(rule_b, NFTNL_EXPR_NAT_REG_PROTO_BASE))
+ print_err("Expr NFTNL_EXPR_NAT_REG_PROTO_BASE mismatches");
if (nftnl_expr_get_u32(rule_a, NFTNL_EXPR_NAT_FLAGS) !=
nftnl_expr_get_u32(rule_b, NFTNL_EXPR_NAT_FLAGS))
print_err("Expr NFTNL_EXPR_NAT_FLAGS mismatches");
@@ -77,6 +80,7 @@ int main(int argc, char *argv[])
nftnl_expr_set_u32(ex, NFTNL_EXPR_NAT_REG_ADDR_MAX, 0x5134682);
nftnl_expr_set_u32(ex, NFTNL_EXPR_NAT_REG_PROTO_MIN, 0x6124385);
nftnl_expr_set_u32(ex, NFTNL_EXPR_NAT_REG_PROTO_MAX, 0x2153846);
+ nftnl_expr_set_u32(ex, NFTNL_EXPR_NAT_REG_PROTO_BASE, 0xbf3c0fbf);
nftnl_expr_set_u32(ex, NFTNL_EXPR_NAT_FLAGS, 0x4213683);
nftnl_rule_add_expr(a, ex);
--
2.39.2
